Interelectrode coupling in high-frequency electric discharge devices



E. D. MCARTHUR 2,543,637 INTEEELECTRCDE CouPLINC IN HIGH-FREQUENCY ELECTRIC DISCHARGE DEVICES Filed June 4, 1946 Inventor-1 .Elmer D. McArthur',

His Atborheg.

Patented Feb. 27, 1951 INTERELECTRODE COUPLING IN HIGH-FRE- QUENCY ELECTRIC DISCHARGE DEVICES Elmer D. McArthur, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application June 4, 1946, Serial No. 674,193

Claims. 1

My invention relates to electric discharge devices and more particularly to improved electric discharge devices particularly adapted for operation as oscillators or amplifiers at high frequencies.

In the operation of electric discharge devices as oscillators, energy is fed back from the output circuit to the input circuit with the feed-back voltage having the proper phase relation and magnitude to sustain the oscillations. Many arrangements have been provided in the prior art for controlling the phase and magnitude of the feed-back voltage. For example, the feed-back has been accomplished electromagnetically by a path external to the device having the proper impedance or electrical length to insure the proper phase relation and magnitude of the feedback voltage. Devices having planar electrodes of adjustable spacing have also been employed; however, these latter devices have possessed many structural disadvantages.

In accordance with my invention, I provide an improved electric discharge device which provides for the coupling of variable impedance between the appropriate electrodes of the device to provide the proper feed-back of energy to sustain oscillations. The same structure provides a circuit fcr stabilizing the device when operated as an amplifier.

It is an object of my invention to provide a new and improved electric discharge device.

It is another object of my invention to provide a new and improved coupling between the electrodes ci an electric discharge device to provide for the feed-back of energy from the output to the input circuit of the device when operated as an oscillator.

It is a still further object of my invention to provide anew and improved electric discharge device including improved means for coupling between the input and output electrodes of the device.

Further objects and advantages of my invention will become apparent as the following description proceeds, reference being had to the accompanying drawing, and its scope will be pointed out in the appended claims. In the drawing, Fig. 1 is a sectional view of an electric discharge device and cavity oscillator circuit embodying my invention; Fig. 2 is a sectional view of a modified form of a portion of the device and circuit of Fig. l; Fig. 3 is a sectional view of an electric discharge device embodying a modification of my invention, and Fig. 4 is asectOnal view of an electric discharge device illustrating a still further modification of my invention.

Referring now to Fig. 1 of the drawing, I have shown my invention embodied in an electric discharge device of the disk-seal type including an envelope comprising a cylindrical member I having an inwardly directed ange 2 to the upper surface of which is sealed a hollow cylindrical insulator 3. A disk-like metal terminal ll is sealed to the upper end of the cylinder 3 and provides a support for an apertured planar grid mesh 5. The anode B of the device is supported from a metal disk 1 supported from the disk I3 by a hollow glass cylinder 8 which is sealed at its opposite ends to the disks 4 and 1.

As illustrated in the drawing, the grid 5 extends transversely of the envelope and is provided at its center with an aperture. The anode 6 extends within the envelope and is provided with a generally annular planar active surface 9 arranged in spaced parallel relation with respect to the grid 5. The cathode of the device is provided by a generally annular member I0 of U-shaped cross section which is supported in inverted relation with the base of the U, -providing the active surface of the cathode and extending substantially parallel to the grid mesh 5. As illustrated in the drawing, one leg of the U-shaped member I0 is supported from the inwardly directed nange 2 of the envelope member I by an upwardly extending cylindrical flange II. The inner leg or side wall of the cathode member I0 is supported by a cylindrical conductor I2 of smaller diameter than the ange II which is supported concentrically therewith and extends through a header I3. The header is welded or otherwise joined at its outer edge to the lower end of the cylindrical envelope member I.

As will be readily understood, the cathode is adapted to be heated to electron emissive temperature by a heater coil I4 supported within the cathode member I I and having one terminal connected to a lead-in conductor I5 sealed through the header I3 by a body of glass designated by the numeral I6. The other terminal I4 of the heater may be joined directly to the flange I I.

The cylindrical conductor I2 connected with the cathode provides the outer conductor of a concentric transmission line including an inner conductor I1 which extends concentrically through conductor I2 and through the aperture in the grid mesh 5. Conductor I1 terminates in a disk I3 which capacitively couples the conductor with the anode of the device. As illustrated, suitable insulating disks IB support conductor I1 within the conductor I2 and seal it through the envelope of the device.

In order to control the impedance of the circuit provided between the anode 6 and the cathode I by means of the concentric transmission line including conductors I2 and I1, I provide an extension of this concentric line including an outer conductor and an inner conductor 2l which are adapted to be short circuited at different distances from the discharge device by a plunger 22. It will be readily understood that movement of the plunger 22 adjusts the impedance of the circuit between the anode and cathode of the device. y

In Fig. 1 I have shown resonators of the concentric type connected with the anod-e-grid and grid-cathode circuits and which provide the input and output circuits of the device when used as an oscillator of the grounded grid type. As illustrated, concentric cylinders 23, 24 and 25 of progressively increasing diameter resiliently engage the anode 6, the grid terminal 4 and the cylinder I which is connected with the cathode to provide anode-grid and grid-cathode cavities.

These cavities extend in the same longitudinal direction and are tunable by adjustable plungers 26 and 21 extending into the upper ends thereof. In order to operate the modification of my invention shown in Fig. 1, it is necessary to prevent the cavity structures from short circuiting the various electrodes of the discharge device with respect to direct current voltages, while leaving the circuits intact with resp-ect to high frequency voltages. To this end a thin ring of insulation is interposed between the cylinder 25 and the cathode terminal I of the device. In a similar manner an apertured disk I of insulation is interposed between the end of conductor 23 and terminal 1 and a cylindrical ring 23' of insulation is interposed between the cylinder 23 and the anode 6. These insulating members and the bounding conducting surfaces provide by-pass capacitors which connect the entire resonant structure together with respect to high frequency voltages.

It is believed that the manner in which the embodiment of my invention described in Fig. 1 operates as an oscillator will be readily understood by those skilled in the art. With a suitable direct current voltage impressed between the anode 6 and the cathode terminal I, the device may be made to oscillate provided the constants of the input cavity, defined by conductors 24 and 25, and the output cavity, dei-ined by conductors 23 and 24, are properly adjusted and that the feedback between these circuits is properly adjusted. In accordance with an important aspect of my invention, this feedback is controlled within the device by controlling the coupling between the anode and cathode. In the illustrated embodiment, this is accomplished by the concentric circuit including conductors I2 and I1 and the extending conductors 20 and 2|. As is well understood, the capacity member I8 couples the transmission line with the anode, and the conductor I2 is connected directly with the cathode. By adjusting the position of plunger 22, the impedance of the connection between the anode and cathode is adjusted and by proper positioning of plunger 22 optimum conditions for oscillation are readily obtained.

, In Fig. 2 I have shown a modified form of the electric discharge device shown in Fig. 1in which the adjustable section of the coupling transmission line engages the interior of the transmission line section built into the tube. All parts of the device shown in Fig. 2 correspond directly to parts of Fig. 1 and the same reference numerals have been used to designate these parts. The numerals have been primed in those cases where the dimensions or shape of the parts differ. In Fig. 2 the outer conductor I2 of the concentric line coupling the anode and cathode is outwardly ared at 28 at the lower end and joined to the inside of the header I3. With this construction the extension 20 of the conductor I 2' engages the inside surface of the ilared portion of the conductor within the base.

In Fig. 3 I have shown a modification of my invention in which the concentric circuit coupling of the anode and cathode within the tube extends from the anode end of the tube and is coupled directly with the cathode instead of capacitively by the member I8, as shown in Fig. 1. Referring now to Fig. 3, the discharge device is in general similar to that shown in Fig. 1 but with the electrode terminals of progressively increasing diameter from the cathode to the anode end of the device rather than from the anode to the cathode as shown in Fig. 1. The anode, as illustrated, is constructed as a single metal member 29 of generaly cylindrical form and having an apertured disk-like portion 30 to one side of which is sealed a cylinder of glass 3|. The anode surface proper designated by the numeral 32 is of annular shape and is provided by the inner end of a cylindrical portion 33 of the anode member 29 which extends within the glass cylinder 3I and concentrically mounted therewith. The grid 34 of the device is provided by an apertured mesh, as in the case of the modification shown in Fig. l, and is supported by an annular metal disk terminal 35 sealed to the other end of the glass cylinder 3I. The cathode of the device is provided by a sheet metal member 36 providing a generally annular and planar active surface 31 extending parallel to the active surface of anode 32 and grid 34. The member 36 is depressed in the central portion to dene an internal channel within which the heater element 38 is received. The cathode member 36 is supported by a conducting cylinder 39 which is sealed to the envelope by a body of glass 40. A metal cylinder 4I sealed to the outer surface of the glass body 40 and joined to the grid terminal 35 completes the envelope of the device. The lower end of the cathode supporting the cylinder 39 is closed by a header 42 through which one of the heater leads 43 is sealed. The other heater lead 44 may be'joined directly to the cathode supporting cylinder 39.

It will be readily understood by those skilled in the art that anode-grid and grid-cathode cavities may be provided in the same manner as illustrated in connection with Fig. 1. In accordance with my invention, I also provide a circuit of distributed characteristics connected directly between the cathode and the anode. As shown in the drawing, a conductor 45 is joined to the central portion of the cathode member 36 and extends concentrically with the envelope of the device, through the apertured grid, a central bore 46 in the anode, and is supported exteriorly of the envelope by insulating disks 41 which are sealed between the conductor 45 and a concentric outer conductor 48 which is joined to the anode member 29 and forms an extension of the passage 43.

With a device constructed as shown in Fig. 3, it is apparent that the anode-gridgridcathode and anode-cathode 'circuits are all readily accessible for the connection of tuned circuits s o that the input and output circuits may be connected to any desired combination of these terminals and a tuned circuit connected with the terminals not connected in both the input and output circuits to provide the feedback required for operation of the device as an oscillator or for stabilizing the operation of the device as a high frequency amplifier. For example, if the input circuit is connected between the grid and cathode terminals and the output circuit is connected betweenthe grid and anode terminals, the circuit connected between the anode and cathode of thedevice provides the feed-back coupling. It will be understood that the concentric line including conductors 45 and 48 may be tuned by an adjustable plunger (not shown)` such as illustrated in connection with Figs. 1 and 2. The direct coupling of conductor 45 with the cathode, as shown in Fig. 3, is preferred over the arrangement shown in Fig. 1 in those cases where it is intended to employ the circuit provided by these conductors as the output circuit of the system.

In Fig. 4-I have shown still a further embodiment of my invention which electrically is very similar tothat shown in Fig. 3 but Which employs cylindrical electrodes instead of the generally planar type of electrodes employed in the modifications previously described. In the modication shown in Fig. 4,parts corresponding to parts of Fig. 3 have been designated with the same reference numerals, the numerals being primed in those instances where the' shape or dimensions of the parts are somewhat different. As shown in Fig. 4, the active surface of the anode member 29 is provided by the surface bounding the passage 46. The grid is in the form of an open helix 49 supported from the grid terminal 35 by a plurality of Side rods 49. The cathode is supported from the cathode supporting cylinder 39 and takes the form of a sleeve 50 which is closed at its upper end. The inner conductor 45 of the anode-cathode transmission line is joined to the upper end of the cathode, preferably by a section of low heat conducting capacity illustrated at 5I. As illustrated, the heater element 52 of the cathode has one terminal connected directly with the cathode 50 and the other terminal connected with a lead-in conductor 43 supported within the cathode supporting cylinder 39. The operation of the device of Fig. 4 `is essentially the same as that described in connection kwith Fig. 1.

In the yoperation of the embodiments of my invention described above it is apparent that the impedance of the coupling between the combination of electrodes not employedin the input and output circuits of the device as an oscillator may be adjusted to control the feed-back voltage, and in this way to control the operation of the oscillator. In the arrangements shown in Figs. v3 and 4 it will -be apparent that the cathode-grid terminals may be connected with an input circuit, the anode-grid terminals with an output'. circuit, and the anode-cathode terminals provided by the conductors 45 and 48 employed for adjusting the feedback. In an alternative circuit, such as is commonly referred to as a cathode return circuit, the input circuit may be connected to the grid-cathode terminals, the output circuit to the anode-cathode terminals provided by the conductors 45' and i118', and the feed-back voltage controlled by a circuit connected with the anode-grid terminals. Thus the constructions shown in Figs. 3 and 4 render accessible the high frequency terminals of all of the electrodes in such a manner that any desired combination of the anode-grid, grid-cathode and anode-cathode circuits may be employed.

While I have shown and described particular embodiments of my invention, it will be apparent to those skilled in the art that changes and modifications may be made without departing from the features of my invention, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is: 1. An electric discharge device comprising an anode structure and a cathode structure, including opposite planar active surfaces, one of said structures defining an elongated passage extending generally perpendicular to the plane of said surface, a control grid interposed between said active surfaces provided with an opening in alignment with said passage, a conductor supported in said passage in insulated relation with respect to the bounding surfaces thereof and electrically coupled to the other of said electrode structures, said conductor and the bounding surface of said passage providing a concentric circuit, and means coupled to said concentric circuit for short circuiting the conductors of said concentric circuit at dilerent points along the length thereof to control the impedance between the anode and cathode of said device.

2. An electric discharge device comprising a pair of principal electrodes including an anode and a cathode, one of said principal electrodes having an aperture therein, a hollow conductor connected with said one of said electrodes around said aperture and extending away from the other of said electrodes, a grid interposed between said principal electrodes and provided with an aperture, an elongated conductor supported within and in insulated relation with respect to said hollow conductor and providing a concentric transmission line section, said elongated conductor extending through the aperture in said grid and coup-led at one end to said other principal electrode.

3. An electric discharge device comprising an anode, a cathode and a control electrode, an envelope enclosing said electrodes and including three conductive members connected respectively with said anode, cathode and grid and providing externally accessible terminals therefor, conductive structures coupled respectively with said terminals and providing input and output resonators for said device, and additional conductors supported in concentric relation and providing a concentric transmission line section connected electrically with said anode and said cathode independently of said terminals.

4. An electric discharge device comprising a pair of principal electrodes including an anode and a cathode, a control electrode interposed between said principal electrodes, an envelope enclosing said electrodes and including conductive members connected respectively with said anode, cathode and control electrode for providing externally accessible terminals for the named electrodes, one of said principal electrodes having an opening therein, and a conductor supported in said opening in spaced relation with the walls defining said opening and providing a concentric transmission line section, said conductor being electrically coupled with the other of said principal electrodes.

5. An electric discharge device comprising a pair of principal electrodes including an anode and a cathode, a control electrode interposed between said principal electrodes, an envelope enclosing said electrodes and including conductive members connected respectively with said anode, cathode and control electrode and providing externally accessible terminals for connection with grid-cathode and grid-anode circuits, one of said principal electrodes having a passage formed therein, and a conductor supported in said passage in spaced relation with respect to the walls dening said passage and providing a concentric transmission line section, said conductor being electrically coupled with the other of said principal electrodes and cooperating with said one of said principal electrodes to provide concentric terminals for said transmission line section.

6. In combination, an electric discharge device including a pair of principal electrodes, a control electrode interposed bei-Ween said principal electrodes, space resonant circuits connected respectively between one of said principal electrodes and said control electrode and the other of said principal electrodes and said control electrode, one of said principal electrodes having a passage formed therein, a conductor supported concentrically within said passage in spaced relation with respect to the Walls defining said passage and cooperating with the walls defining said passage to provide a concentric space resonant circuit coupled to said principal electrodes, and means for tuning said last-mentioned space resonant circuit to control the feedback between said firstnamed circuits.

'7. An electric discharge device comprising a pair of principal electrodes including an anode and a cathode, an apertured control electrode interposed between said principal electrodes, an envelope enclosing said electrodes and including conductive members connected respectively with said anode, cathode and control electrode for providing externally accessible terminals for the named electrodes, one of said principal electrodes having a passage therein, and an elongated conductor supported in said passage in spaced relation with respect to the walls dening said passage and providing a concentric transmission line section, said conductor extending through the aperture in said control electrode and coupled with the other of said principal electrodes.

8. An electric discharge device comprising a pair of principal electrodes having planar active surfaces including an anode and a cathode, an apertured planar control member interposed between said principal electrodes, an envelope enclosing said electrodes, conductive members sealed through said envelope and connected respectively with said anode, cathode and control electrode for providing externally accessible terminals for the named electrodes, one of said principal electrodes having a passage therein, and a conductor supported in said passage in spaced relation with the Walls defining said passage and extending through said aperture, said conductor and the bounding surface of said passage providing a concentric transmission line coupled between said principal electrodes.

9. In combination, an electric discharge device comprising a plurality of electrodes including an anode, a cathode and a control electrode interposed between said anode and cathode, an envelope enclosing said electrodes and including conductive members connected respectively with said anode, cathode and control-electrode and providing externally accessibleterminals therefor, a space resonant input circuit coupled electrically to the terminals connectedwith said cathode and control electrode,a space resonant output circuit coupled electrically to -the terminals connected with said anode and one of the other two electrodes, and a space resonant circuit connected electrically to the anode and the remaining one of said other two electrodes independently of said terminals for controlling the feed-back impedance between said anode and saidremaining electrode.

10. In combination, an electric discharge device comprising a plurality of electrodes including an anode, a cathode and a control electrode interposed between said anode and cathode, an envelope enclosing said electrodes and including conductive members connected respectively with said anode, cathode and control electrode and providing externally accessible terminals therefor, a tuned input circuit connected between the terminals connected with said cathode and control electrode, a tuned output circuit connected between the terminals connected with said anode and one of the other two electrodes, and a tunable circuit connected between the anode and the remaining one of said other two electrodes independently of said terminals for controlling the feed-back impedance between said anode and said remaining electrode.

Y ELMER D. MCARTHUR.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,157,952 Dallenbach May 9, 1939 2,400,753 Haeff May 2l, 1946 2,408,927 Gurewitsch Oct. 8, 1946 2,411,424 Gurewitsch Nov. 19, 1946 2,433,634 Stone Dec. 30, 1947 2,445,077 Nergaard et al July 13, 1948 2,461,125 Nergaard Feb. 8, 1949 

